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An Assessment of the Solar and Space Physics Aspects of NASA's Space Science Enterprise Strategic Plan (report) An Assessment of the Solar and Space Physics Aspects of NASA's Space Science Enterprise Strategic Plan INTRODUCTION Recently, NASA's Office of Space Science (OSS) released its Space Science for the 21st Century: The Space Science Enterprise Strategic Plan, (the Enterprise Plan),1 which includes a summary of planned solar and space physics activities to be initiated by NASA in the period 1995 to 2000. Publication of the Enterprise Plan occurred prior to the release of CSSP/CSTR's report, A Science Strategy for Space Physics (the Science Strategy).2 The purpose of this short report is to comment on the extent to which the OSS Enterprise Plan corresponds to the recommendations made in CSSP/CSTR's Science Strategy for scientific research in solar and space physics during the coming decade. CSSP/CSTR's intent in this assessment is to identify, for NASA's benefit, a more comprehensive agenda of solar and space physics activities that might be included in updates to the Enterprise Plan. MENU NOTICE SUMMARY OF CSSP/CSTR'S SCIENCE STRATEGY MEMBERSHIP REPORT APPENDIX CSSP/CSTR's Science Strategy recommends the major directions for scientific research in space physics for the coming decade. As a field of science, space physics has passed through the stage of simply looking to see what is out beyond Earth's atmosphere. It has become a "hard" science, focusing on understanding the fundamental interactions between charged particles, electromagnetic fields, and gases in the natural laboratory consisting of the galaxy, the Sun, the heliosphere, and planetary magnetospheres, ionospheres, and upper atmospheres. The several subfields of space physics share the following objectives: To understand the fundamental laws or processes of nature as they apply to space plasmas and rarefied gases both on the microscale and in the larger, complex systems that constitute the domain of space physics; To investigate the links between changes in the Sun and the resulting file:///C|/SSB_old_web/sspaspec.html (1 of 8) [6/18/2004 2:05:05 PM]

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An Assessment of the Solar and Space Physics Aspects of NASA's Space Science Enterprise Strategic Plan (report) effects at Earth, with the eventual goal of predicting the significant effects on the terrestrial environment; and To continue the exploration and description of the plasmas and rarefied gases in the solar system. CSSP/CSTR's Science Strategy identifies five scientific topics to be addressed in space physics research in the coming decade: 1. Mechanisms of solar variability. The Sun is a variable star on time scales of milliseconds to centuries or more. Its emissions vary throughout the electromagnetic spectrum, as do its particle (thermal plasma and energetic) outputs. The solar magnetic field, generated in the Sun’s interior, holds many of the keys to understanding these variations that influence Earth’s space environment and its climate. 2. The physics of the solar wind and the heliosphere. The solar wind, the extended atmosphere of the Sun that reaches beyond the solar system, is responsible for a host of effects on all planetary bodies and on the local interstellar medium. It is still not known what drives this wind and its variations. Extreme solar-wind disturbances cause the most severe "space weather" around Earth. 3. The structure and dynamics of magnetospheres and their coupling to adjacent regions. The distortions of planetary magnetic fields caused by their interaction with the solar wind are responsible for the "magnetospheric" effects that contribute to space weather. All manifestations of this coupling, from the auroral emissions that appear in the polar regions of the upper atmosphere to the radiation environments of our Earth satellites, vary continually in response to the changing boundary conditions produced by the Sun. This complex, three- dimensional system is also constrained by the atmosphere and ionosphere at its innermost boundary. Synergistic observations and modeling efforts are revealing the manner in which these near-planet space systems work. 4. The middle and upper atmospheres and their coupling to regions above and below. The lower boundary region of near-Earth space is constantly buffeted by variable energy inputs from the Sun and the magnetosphere above, and from the lower atmosphere below. Significant deficiencies exist in our knowledge of the internal workings of this region and its role in determining magnetospheric response to solar wind variations. These deficiencies result from both the difficulty of making measurements there and the region’s intrinsic complexity. 5. Plasma processes that accelerate very energetic particles and control their propagation. Galactic cosmic rays are samples of matter from outside the solar neighborhood that provide clues to subjects ranging from particle acceleration processes in the cosmos to the physics of stellar interiors. file:///C|/SSB_old_web/sspaspec.html (2 of 8) [6/18/2004 2:05:05 PM]

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An Assessment of the Solar and Space Physics Aspects of NASA's Space Science Enterprise Strategic Plan (report) For each of these topics, CSSP/CSTR’s Science Strategy presents the scientific background, discusses why the topic is important, describes the current program for research on the topic, and then recommends high-priority research activities for the future. As the Science Strategy points out, "The specific programs required to obtain answers to the questions raised under each of the [above] key topics . . . are quite different. However, they are united by four common elements or themes that the CSSP and the CSTR consider to be the most important research emphases for space physics in the next decade."3 These themes, paraphrased from the Science Strategy (pp. 6-7), are as follows: 1. Complete currently approved programs. The space physics community must reap the benefits of the nation’s investment in existing approved programs by enhancing data analysis and interpretation efforts and by supporting essential observational programs that require long-duration databases. A stable program of research permits the most efficient management and execution of high-priority research. Older missions that are productive and competitive in their scientific return should not be terminated prematurely. In addition to the obvious scientific return, ongoing programs provide the basis for developing future research directions. 2. Exploit existing technologies and opportunities to obtain new results in a cost-effective manner. Much technology is already in place to take the next observational steps required to address many of the important questions outlined in CSSP/CSTR’s Science Strategy. However, adaptation of instrumentation to the new generation of smaller spacecraft requires special support. Ground-based facilities, suborbital platforms, and opportunities for space physics payloads to "hitchhike" on other spacecraft are valuable means for achieving space physics science objectives, as are extended and/or redirected missions. 3. Develop the new technology required to advance the frontiers of space physics. To achieve several high-priority objectives, or to lower the cost of projects, the limits of technology must be pushed. Areas for development include global and high-resolution imaging techniques, high-temperature-tolerant devices for operation near the Sun, and methods to enable access to difficult-to-reach regions of the middle atmosphere. 4. Support strongly the theory and modeling activities vital to space physics. The importance of modeling and theory in both stimulating and interpreting space physics measurements must be recognized. From models of space weather to models of the microscopic behavior of plasmas involved in the triggering of solar flares and magnetospheric disturbances, state-of-the-art work is being done that increases our scientific understanding in step with measurements made in space, while developing the necessary framework for future missions. file:///C|/SSB_old_web/sspaspec.html (3 of 8) [6/18/2004 2:05:05 PM]

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An Assessment of the Solar and Space Physics Aspects of NASA's Space Science Enterprise Strategic Plan (report) CSSP/CSTR's COMMENTS ON NASA's OSS ENTERPRISE PLAN NASA's OSS Enterprise Plan begins by describing the foundation of its space science strategy in terms of its relevance to the United States, its mission and goals, its key assumptions and considerations, and the principles on which the plan is based. The CSSP and the CSTR recognize the thought and effort that were put into formulating these introductory sections, which generally give a clear sense of what lies behind NASA's space science endeavor. With regard to the plan's degree of consistency with the research directions emphasized in CSSP/CSTR's Science Strategy, released after publication of the Enterprise Plan, the CSSP and the CSTR note the following: The Enterprise Plan's section titled "Sun-Earth-Heliosphere Connection" is in accord with CSSP/CSTR's strategy in many respects, especially in its acknowledgment of and support for the original three space physics solar-terrestrial probe mission concepts (TIMED, HESI, and MI4) that were developed over the past few years through broad-based space physics community prioritization exercises. Whether or not all of these missions are realized as solar-terrestrial probes, their science goals are timely and are key to advancing the Solar Connections Program. Indeed, funding for the TIMED mission began this year, and the recently selected MIDEX mission, IMAGE, addresses many of the science goals envisioned for MI. However, to accomplish its scientific objectives, the HESI mission must be launched during the peak of solar activity. That is no longer possible using either solar-terrestrial probes or the MIDEX line, and therefore requires an alternate strategy if it is to be carried out during this solar cycle. The explicit commitment in the Enterprise Plan to NASA's participation in the National Space Weather Program5 is in line with one of the Science Strategy's overall objectives for space physics. Indeed, many missions currently under way to explore solar connections, as well as missions in the concept phase, will provide the key information that will be needed for future space weather research and development projects, including space weather forecasting services. This example of the broad relevance of the solar connections missions deserves greater emphasis in the Enterprise Plan, especially in view of the increasing commercial use of space and the projected international space station activities. NASA's OSS future mission plan (see table on p. 12 of the Enterprise Plan), including solar probe, contains the basic mission elements necessary for accomplishing the goals outlined in CSSP/CSTR's Science Strategy, but other missions in the solar probe class should also be identified. For example, a Mercury orbiter and an interstellar probe are long-awaited space physics missions that have been repeatedly identified in National Research Council reports6,7 as the means to investigate the ionosphere's role in magnetospheric behavior (Mercury has essentially no ionosphere, but has a magnetosphere), and file:///C|/SSB_old_web/sspaspec.html (4 of 8) [6/18/2004 2:05:05 PM]

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An Assessment of the Solar and Space Physics Aspects of NASA's Space Science Enterprise Strategic Plan (report) to explore the nature of the heliosphere's interface with the galaxy, respectively. These missions and others are mentioned below. RECOMMENDATIONS FOR ADDITIONS TO NASA's FUTURE PLANS FOR EXPLORATION OF SUN-EARTH-HELIOSPHERE CONNECTIONS Overall, the scientific priorities summarized in the "Sun-Earth-Heliosphere Connections" portion of the Enterprise Plan compare favorably with those expressed in CSSP/CSTR's Science Strategy. However, the CSSP and the CSTR recommend that subsequent updates of the solar and space physics portion of NASA's Enterprise Plan mention the following: The innovative suborbital program (e.g., Flare Genesis balloon observations of evolving solar active regions, sounding rocket campaigns in support of the ISTP program, campaigns to observe "sprites" and "jets"), with clear acknowledgment of the contributions the suborbital program makes to the instrument capabilities of the solar connections endeavor, including both training and hardware development; The diverse and productive space physics Explorers—SAMPEX, ACE, FAST, and eventually TRACE and IMAGE, as well as the STEDI missions (TERRIERS and SNOE)—emphasizing how Explorers are especially suited to achieving focused space physics objectives in creative and effective ways. The adoption of open data policies and the major outreach and educational components of the space physics Explorers are also noteworthy; The unprecedented combination of the ISTP GGS (Wind, Polar), Geotail, and SOHO missions with supporting ground-based observing and theory programs, pointing out their connection to the interagency National Space Weather initiative and the importance of their operation into the next solar maximum; The expected contributions from the rapidly developing field of helioseismology. Ground-based and SOHO helioseismic observations show a potential for improving understanding of the interior of the Sun and the origins of solar and stellar activity; The expected contribution of TIMED extreme ultraviolet wavelength measurements to studies of solar variability and its effects on the atmosphere; Recent measurements of cosmic rays from suborbital platforms, with a description of how such data are helping to elucidate nucleosynthesis; and file:///C|/SSB_old_web/sspaspec.html (5 of 8) [6/18/2004 2:05:05 PM]

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An Assessment of the Solar and Space Physics Aspects of NASA's Space Science Enterprise Strategic Plan (report) Space physics discoveries from the Galileo mission at Jupiter, emphasizing especially what researchers are learning from comparative planetology studies. In addition, the Enterprise Plan should discuss expectations from the Rosetta-Champollion and Cassini missions for space physics. It should also summarize the breakthroughs in understanding that are being made possible through theory and modeling programs and ground-based observations. The CSSP and the CSTR also recommend that the solar and space physics community be marshalled to provide the latest information related to the above activities for inclusion in the next version of the Enterprise Plan. In addition, the CSSP and the CSTR recommend that an updated plan's description of future programs include the following: Campaigns focused on study of how the Sun's magnetic field is generated and what causes solar variability. Unraveling the origin of the solar magnetic field is a grand challenge for space physics with astrophysical implications. To enable understanding of solar activity in all its forms, such campaigns must include spacecraft in addition to a solar probe (e.g., a stereoscopic solar imager), as well as suborbital and ground-based instrument development, and supporting theory and modeling. Missions utilizing multipoint measurements with clusters of small spacecraft to explore three-dimensional structure and to distinguish temporal and spatial domains, particularly at boundary layers in space plasmas. These missions both push the limits of technology (particularly the miniaturization of instruments and spacecraft subsystems) and provide essential information for understanding how energy is transferred between regions of space. The aborted launch in June 1996 of Ariane-5 and subsequent loss of the Cluster mission component of the ISTP adds to the importance of making new efforts in this area. Missions to probe middle-atmosphere dynamics, making use of innovative techniques to gain in situ access to that region. (However, problems experienced with the Tethered Satellite System experiment are likely to affect future plans for exploration using the space shuttle.) Missions to solar system bodies that interact differently with the solar wind than does Earth, thereby providing lessons in comparative planetology from a solar connections perspective (e.g., "magnetospheric" and aeronomical exploration of Mercury, Mars, and Pluto can help reveal how Earth's strong planetary field and ionosphere determine its unique space environment). Missions to interstellar space, beyond the heliosphere. This frontier between the realms of solar and space physics and astrophysics is likely to yield many surprises. file:///C|/SSB_old_web/sspaspec.html (6 of 8) [6/18/2004 2:05:05 PM]

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An Assessment of the Solar and Space Physics Aspects of NASA's Space Science Enterprise Strategic Plan (report) Programs that bring together the astrophysical, planetary, Earth science, and space physics communities in a coordinated effort to solve the problems of solar systems on a more general level (e.g., the interactions between planets and their stars, and between stellar winds and the surrounding interstellar medium, should also be parts of the "origins" theme science within the recently restructured OSS). In summary, the CSSP and the CSTR find that the solar and space physics aspects of NASA's present Science Enterprise Strategic Plan are much in line with research recommended in CSSP/CSTR's Science Strategy. At the same time, the CSSP and the CSTR recommend that the above new elements be included in NASA's next vision for exploration of the Sun-Earth-heliosphere connection. NOTES 1. National Aeronautics and Space Administration, Space Science for the 21st Century: The Space Science Enterprise Strategic Plan, Washington, D.C., September 1995. 2. Space Studies Board and Board on Atmospheric Sciences and Climate, National Research Council, A Science Strategy for Space Physics, National Academy Press, Washington, D.C., 1995. 3. Space Studies Board and Board on Atmospheric Sciences and Climate, National Research Council, A Science Strategy for Space Physics, National Academy Press, Washington, D.C., 1995, p. 6. 4. Acronyms are spelled out in the appendix. 5. The National Space Weather Program is a recently initiated interagency endeavor to coordinate and exploit research related to the coupled solar-terrestrial system and its consequences for Earth's environment. 6. Space Studies Board and Board on Atmospheric Sciences and Climate, National Research Council, A Science Strategy for Space Physics, National Academy Press, Washington, D.C., 1995. 7. Task Group on Solar and Space Physics, Space Science Board, National Research Council, Space Science in the Twenty-First Century: Imperatives for the Decades 1995-2015, National Academy Press, Washington, D.C., 1988. file:///C|/SSB_old_web/sspaspec.html (7 of 8) [6/18/2004 2:05:05 PM]